This invention is related in general to digital networks and more specifically to the switchover from one processor to another in a route processor system by using state preservation to prevent packet loss.
Mobility networks, such as wireless networks, are a valuable alternative to fixed (e.g., wired) networks. Mobility networks provide advantages by allowing end users to move about freely, or roam, within a coverage area. Users can operate small portable devices such as laptops, personal digital assistants (PDAs), cell phones, etc., and still remain connected to a network such as the Internet, local area network (LAN), etc., at any point within the coverage area. Today's mobility networks are becoming better at quickly establishing a network connection and maintaining the network connection seamlessly as the user moves from one access point to another.
One critical single point of failure in a mobility network is the route processor. The route processor can include hardware components and software processes for creating and maintaining routing-table information for access points, user devices and other nodes in the network. The route processor is responsible for updating other routing devices or processes by providing routing table synchronization. If the route processor goes down (e.g., due to a malfunction) then the devices in a large part of the network can lose connection and have to re-establish their presence on the network by reconnecting, re-authenticating and possibly performing other steps.
One way to prevent connection loss due to route processor failure is to use two processors within a single route processor. A first, active, processor performs the route processor's functions and sends all routing table updates to a second, standby, processor, also within the route processor system. Upon failure of the active processor, control is turned over (a “switchover”), to the standby processor which then becomes the active processor. Although this approach helps to reduce the number of lost connections and other disruption to the network, the latency of performing routing table updates and other messaging and processing delays can mean that at the time of switchover the standby processor's routing table is not an exact copy of the active processor's routing table. In such cases, some connections may need to be reset in order to establish proper routing or other measures taken to ensure reliable and secure operation of the network.